On Mon, Nov 06, 2023 at 09:12:56PM -0800, Eric Pilmore wrote: > On Mon, Nov 6, 2023 at 12:46 PM Matthew Dharm > <mdharm-usb@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > Special MMIO reservation in BIOS is not required if a device in your > > PCIe tree, such as a Broadcom Gen4 or Gen5 switch device, can reserve > > address space via "synthetic mode" for missing devices. > > > > Matt > > Yes, I'm familiar with Synthetic Mode (or Synthetic Endpoints), but > that's simply creating a dummy device to fool the BIOS into > effectively putting aside some amount of MMIO space. And that works > great so long as what you want to dynamically add fits within that > reserved space. I guess I was looking for something more flexible > where I didn't need to know a priori the "size" of what I wanted to > add in. Presumably this would require some kind of rebalancing of the > address assignments within the PCIe tree/sub-tree, which in turn > likely means temporarily "suspending" I/O activity, at least across > some portion of the I/O tree, while addresses move around. No, that is not something that Linux supports at this time. I also don't think that any other operating system supports it either, right? We always said, if someone wants to support this, great, we will be glad to review the patches for adding this type of functionality. But until then, we just rely on the BIOS or other types of hardware to handle this properly for us. thanks, greg k-h
